1. Field of the Invention
The present invention relates to a sealing grommet which holds a wire harness and which is mounted in the through hole of a vehicle panel; and to methods of assembling the sealing grommet, and of forming a waterproof seal within the grommet. The present invention is particularly applicable to a sealing grommet suitable for use with a small diameter wire harness which is produced by a small number of wires, but is clearly not limited thereto and could be applied to many other situations.
2. Background of the Invention
A grommet, formed, for example, from rubber or elastomer, holds a wire harness that extends from a compartment to the exterior of the compartment through a through hole of a vehicle panel. The grommet is fixedly mounted in the through hole to prevent water, etc. from penetrating the compartment through the panel.
A conventional grommet 1, 1xe2x80x2 of this kind as shown in FIGS. 6, 7, 8(A) and (B) is provided with a small diameter tubular portion 1a, 1axe2x80x2 which tightly holds a group of wires and an enlarged diameter tubular portion 1b, 1bxe2x80x2 which continues in a conical tube shape from one end of the small diameter tubular portion 1a, 1axe2x80x2. A panel engagement recess 1c, 1cxe2x80x2 is formed on the outer peripheral surface of the enlarged diameter tubular portion 1b, 1bxe2x80x2. 
As shown in FIGS. 6 and 7, the grommet 1 of this kind (Hereinafter referred to as an engine harness grommet) is generally mounted on an engine compartment wire harness W/H that extends through the through hole on a firewall between engine and passenger compartments. However, as shown in FIGS. 8(A) and (B), a grommet 1xe2x80x2of this kind (Hereinafter referred to as a floor harness grommet) may also be mounted on a floor wire harness W/Hxe2x80x2 that, for example, extends to the mounting area of a fuel tank 4 at the rear of a vehicle, through a lower panel 3 in a luggage compartment 2. The floor wire harness W/Hxe2x80x2 has a group of wires that supply electric power to electrical loads such as a fuel pump and a license lamp. However, since the floor wire harness W/Hxe2x80x2 requires only a limited number of wires, i.e., 5 to 6 wires at maximum, it is smaller in diameter than the engine harness W/H. Accordingly, the floor harness grommet 1xe2x80x2 is equally smaller in size than the engine harness grommet 1.
In order to prevent water from penetrating into the luggage compartment, a tape 5xe2x80x2 is doubly wound on a region outside the luggage compartment from the small diameter portion 1axe2x80x2 of the grommet 1xe2x80x2 to the floor wire harness W/Hxe2x80x2, in the same manner as shown in FIG. 7. However, mere double winding of the tape 5xe2x80x2 does not prevent the ingress of water completely because water may permeate through the gaps between the individual wires of the floor wire harness W/Hxe2x80x2, as well as the gap between the inner surface of the tape 5xe2x80x2 and the outer surface of the wire harness W/Hxe2x80x2.
To improve waterproofing reliability, a sealant can be provided to form a seal between the wires, and, for example, it is known to provide such a sealant (not shown) in the engine harness grommet 1. In this case, the sealant is introduced into the front end opening 1c of the enlarged diameter tubular portion 1b, using a sealant injection nozzle (not shown). However, as described above, since the floor harness grommet 1xe2x80x2 is smaller than the engine harness grommet 1, the front end opening 1dxe2x80x2 of the floor harness grommet 1xe2x80x2, into which the sealant is to be injected by use of the nozzle, is equally smaller than that of the engine harness grommet 1. Consequently, the injection nozzle (not shown) would interfere with the front end opening 1dxe2x80x2 of the floor harness grommet 1xe2x80x2 when the sealant is to be injected. Thus, it would be very difficult to fill the sealant into the floor harness grommet 1xe2x80x2, by inserting the injection nozzle in the conventional manner.
The present invention has been developed after taking the above problems into consideration, and aims to provide a sealing grommet having a construction such that a waterproof seal can be formed between wires of a wire harness with ease and certainty. The present invention further aims to provide methods of assembling the sealing grommet and of forming the waterproof seal.
To solve the above problems, the present invention provides a sealing grommet that includes a grommet body having a sealant reservoir and a sealant drain portion. Specifically, the grommet body includes: an outer peripheral wall; a panel engagement recess formed on the outer surface of the outer peripheral wall and configured for hooking engagement with an aperture of a panel; and an inner peripheral wall extending inwardly of the outer peripheral wall and defining a wire harness insertion aperture inwardly thereof. The sealant reservoir is provided between the inner and outer peripheral walls, and is configured to temporarily store a sealant therein. The drain portion is provided on the inner peripheral wall, and is configured to open upon deformation of the grommet body, thereby permitting the sealant to drain into the wire harness insertion aperture from the reservoir.
With this construction, the sealant can easily permeate between wires of a wire harness within the harness insertion aperture after the drain portion opens. Furthermore, because the need for a sealant injection nozzle can be eliminated, a waterproof sealing operation can be carried out without any difficulties, even if the size of the sealing grommet is small.
According to a preferred embodiment of the present invention, the drain portion is configured to be frangible. Thus, it can be ripped open upon deformation of the grommet body.
In another aspect of the present invention, the grommet body further has a drain actuator portion configured for opening the drain portion upon operation thereof. Thus, the drain portion can be opened effectively. According to another preferred embodiment, the drain actuator portion is in the form of a handle portion that is configured to be readily gripped by the operator and pulled to open the drain portion. Moreover, the handle portion is provided on the inner peripheral wall, and is configured to project into the wire insertion aperture prior to the insertion of the wire harness and to project outwardly of the grommet body after the insertion of the wire harness. Also, the handle portion is positioned in proximity to an opening side where the wire harness extends outwardly from the harness insertion aperture, thereby permitting the handle portion to easily project out of the opening side and to be readily gripped and pulled until the drain portion opens.
Preferably, the drain portion has a frangible thin wall portion configured to be ripped open when the handle portion is pulled away. According to another preferred embodiment, the thin wall portion is formed into a generally V-shaped groove. The thin wall portion may be spaced apart a predetermined distance from the handle portion, and positioned at a location farther away from the opening side than the handle portion.
In a further aspect of the present invention, the outer peripheral wall of the grommet body has a small diameter tubular portion and an enlarged diameter tubular portion that continues in a conical tube shape from a first joined portion of the small diameter tubular portion. The panel engagement recess is formed on the outer surface of the enlarged diameter tubular portion, and the sealant reservoir is formed between an inner peripheral wall and the enlarged diameter tubular portion. Preferably, the inner peripheral wall and the small diameter tubular portion extend substantially concentrically to form double tubular portions, and are configured for releasable engagement with each other. According to a preferred embodiment, the small diameter tubular portion and the inner peripheral wall are separably engaged prior to injection of the sealant, and are permanently fixed together at an engagement area after the injection of the sealant. Accordingly, the sealant reservoir can be sealed effectively to prevent curing of the sealant within the reservoir.
In a further aspect of the present invention, the inner peripheral wall has a foldable tubular portion extending outwardly from a second joined portion of the enlarged diameter tubular portion. The foldable tubular portion can be folded inwardly at a folding-back portion adjacent the second joined portion, and can be extended interiorly of the outer peripheral wall. As a result, the sealant reservoir and the harness insertion aperture can be formed substantially concentrically with respect to the foldable tubular portion. In the sealant reservoir, the sealant is temporarily stored until the drain portion is opened.
Further, the present invention provides a method of assembling the above sealing grommet. First, the foldable tubular portion is folded inwardly at the folding-back portion, and extends interiorly of the enlarged diameter and the small diameter tubular portions so that the foldable tubular portion releasably engages with an inner peripheral surface of the small diameter tubular portion. As a result, the sealant reservoir is formed between the foldable tubular portion and the enlarged diameter tubular portion, with the harness insertion aperture formed inwardly of the foldable tubular portion. Next, the foldable tubular and the small diameter tubular portions are separated to form a sealant injection opening therebetween, and then the sealant is filled into the reservoir through the injection opening. Finally, the injection opening is closed, so that the reservoir can be sealed effectively to prevent curing of the sealant prior to drainage of the sealant into the harness insertion aperture. Therefore, the sealing grommet can be assembled effectively.
According to a preferred embodiment, the small diameter tubular portion is deformed or enlarged outwardly to form the sealant injection opening. Also, to close the opening, the small diameter tubular and the foldable tubular portions are bonded together at an engagement area.
Still further, the present invention provides a method of forming a waterproof seal between wires of a wire harness provided within a wire harness insertion aperture of the above sealing grommet. The sealant injection opening is formed between the small diameter tubular portion and the inner peripheral wall, and the sealant is injected into the reservoir in a similar manner as described above. The small diameter tubular portion and the inner peripheral wall are then permanently fixed so that the reservoir can be sealed effectively to prevent curing of the sealant within the sealant reservoir. After the small diameter tubular portion and the inner peripheral wall are fixed together, the wire harness is inserted through the harness insertion aperture, and a drain actuator portion provided on the inner peripheral wall is actuated, thereby opening the drain portion to permit the sealant to drain into the harness insertion aperture. This ensures that the sealant permeates between individual wires of the wire harness effectively, thereby forming the waterproof seal between the individual wires with certainty. Of course, in the event that the sealant filled grommet is to be used with a wire harness shortly after the sealant is provided in the sealant reservoir, i.e., before the sealant would normally cure without fixing the small diameter tubular portion to the inner peripheral wall, it would not be necessary to fix the small diameter tubular portion to the inner peripheral wall.
According to a preferred embodiment, the drain actuator portion includes a handle portion and the drain portion has a frangible thin portion. In this case, the handle portion projects outwardly of the grommet body after the insertion of the wire harness. Then, the handle portion is gripped and pulled in a direction away from the grommet body until the thin wall portion is ripped open to permit the sealant to drain into the harness insertion aperture. Should the sealant not flow into the aperture smoothly, the enlarged diameter tubular portion may be squeezed or deformed inwardly to facilitate the drainage of the sealant. This deformation operation can be done either manually or mechanically.